Stabilizing glow-discharge tubes



y 9, o. .SCHRIEVER 1,908,191

STABILIZING' GLOW DISCHARGE TUBES Filed Sept. 7, 1927 INVENTOR OTTO SCHRIEVER fld ,dwuo

- A ORNEY Patented May 9, 1933 r UNITED STATES PATENT" OFFICE o'rro soHnIEvEn, or warm, GERMANY; AssIGNon. TO TELnFunxEneEsELnsomE'r a;

run nRaHrLosn rnnnenamnn M. B. 3., or BERLIN, GERMANY STABILIZIENG eLow-mscimnon'runns Application filed September 7,1927, Serial No. 217,974, and imGerniany October 20, 1926. 5 n

This inventionrelates to an arrangement for stabilizing a glow discharge device and relates alsoto circuitsgfor providing this stabilized operation.

" It is well known that-glow-discharge lamps may-be used for the purpose of recording current curves of waves of any occurring shape orform. The lamp is mostly used by passing a direct current equalling one-half of the saturation current through the glow-discharge lamp and superimposing the alternating' current to be recorded upon therdirect current, the mean brightness or brilliancy of the glow-dischargelamp being then nearly constant and equal to'th'e brightness under normal" condition. However, in recording or reproducing pictures in picture-telegraphy work,the idle current (bias or direct current) should be as lowvas ipossible' in order that the mean "brightness at any given time may 'be nearly proportional to the corre- .sponding brightness conditions of theJpic-V ture. Hence the smaller the direct current, the 'more delicate and the finer will be the reproduction of low brightness values. Howlever, itris well knownthat theglow-discharge V "lamp :has the property :to'go-out in the presenceof a definite lower "limiting value of the voltage and therefore of the current, and is only capable of being restarted when :the somewhat higher value of the potential is reached. The 'factthat extinction occurs, and that-distinction l11S=tOfb821113d8 between extinction and starting or striking potentials render @the glow-discharge lamp unsuited for wtoned "pictures, while in the reproduction of 'ipllle black-white contrast pictures :these "drawbacks are less serious in practice.

Among the objectskof my invention are, -'therefore,*to provide an arrangement forstabilizing the burning of a glow-discharge tube which is especially adaptable for. pic- ;ture telegraphy work. 1 :Other objects of my. invention are to provide ,an arrangement whereby it is possible to=superimpose thepicture frequencies in the normal currentjflowinginzthe glow-discharge lampso that the mean brightness of'the lamp "depends upon the mean value ofthe alter V nating currentpotential at any instant.

wave for controllingthe lamps.

Other objects of my invention are to provide in a manner hereinafter set forth a means forstabilizing the burning of a glowclischargeilamp which i'sysimple in its construction and arrangement of parts, as :well as $5 a, stabilizing means which is durable, com pact, efficient-in. its useyconveniently. operated,-readily set up and inexpensive to'install.

' The novelieatures which I believe to be characteristic of my invention are set forth in the appended claims-but the invention itself, :however, both as to its organization and method of operation,"itogether with "further objects and advantages thereof, will be bestunderstood by making reference to? the followingdescription read in connection with the accompanying drawing wherein Fig. 1 shows a relatively simple arrangement for stabilizing the lamps V a Fig. 2 illustrates a modification of Fig. 1 in "I which avacuum tube is substituted for the high ohmicresistance; and, Fig. 3 is apreferred 'form'of embodiment somewhat similar to Fig. 2,1out capable of utilizing both halvesof the incoming signal 96 Inorder that the glow-discharge'lamp may beimade,suited also"for thespurpose of recording a toned picture in: picture telegraphy work, accordingto the present invention, and as shown diagrammatically inithe drawing, a

:direct current potential E far above the striking voltage of the glowslamp G' is applied to the "latter by way of afhigh-ohmic resistance W in such a manner that the our-' 7 rent flowing in. circuit I is essentially deter-.

uninedby the relation E WV, which is, in fact,

kept so low by the suitable selection ofithe values of E and W that the light emitted from theglow-dischargelamp under normal 'tery E would 'arise' across the electrodes of the glow-discharge lamp and would thus immediately result .in renewed striking. The picture frequency currents to be recorded or reproduced are fed to the lamp by way of' circuit path II containing a condenser C to shut oil the direct current and being in shunt relationship to path I. Since the resistance l/V has a high ohmic value, the picture frequency currents will choose the way through the glow lamp G and thus cause the, glowdischarge lamp to brighten up in accordance to their particular intensity. It is thus possible to record also very small mean -brightnessvalueswithout the lackof stability of the glow-discharge lamp otherwise present giving rise to distortions. In the work of recording photographs and'the' like 1n which the accurate reproduction even ofthe smallest As shown in grids are provided with such a high negativebiasing potential that the desired 1 small residual current will be allowed to flow. .The current impulses to be recorded are then :most suitably superimposed upon the grid biasing potential of the said tube, for instance, by wa-yoit' the transformer T1". 7

In order to utilize both cycles for controlling the glow-discharge lamp, two tubes having their outputs in parallel as shown in 3,-"may be employed. The" grids of these tubes may be controlled in phase-opposition and biased as described. in connection with Fig. 2. 7

So arranged, the grids of the two tubesare controlled in phase opposition and as shown in the drawing the biasing-means for the grids of the tubes T1 and T2 is connected between the filament and the midpoint of the secondary of the transformer T1". Under such conditions, itthe signal is supplied through the transformer Tr .it may be assumed that the grid of the tube T1, shown to the left of Fig. 3, becomes less negative so that the plate current output from this tube willrise which, due to the fact that the grid of the tube T2 is more negative, will cause a decrease in the output from the tube T2, shown to the .right of Fig. 3. "However,

under such conditions the plate current output of tube T2 does not necessarily decrease in the same proportion that the plate current output of the tube T1 rises. When these .conditions are reversed, due to a reversal of the currentin thev transformer, the grid of the tube T2 is made less negative and thegrid of'the tube T1 becomes more negative, under which condition, there will be an increase in the'plate current output from the tube T2 and a decrease in'the plate current output of the tube T1, but the decrease from normal operating'position of thetube T1 need not be in the same proportion asthe rise in the plate current output'from thetube T2, since the glow tube G will produce varying intensities in glow correspondlng to lncoming signal is brightness values is of extremely great importance, this factor is of eXtremely grea-t value. I Y 4 2,- the' high ohm-resistance may consist also of an amplifier tube whose impulses and since the variation in glow is all that is desired from the system. In order to provide the aims and objects of this inven:

tion, it can be seen that the frequency dou- 1. A system at stabilizing glow-discharge tubes which comprises a glow-discharge lamp, a pair of vacuum tube amplifiershaving their outputs connected inparallel, means for applying a biasing potential tosaid'glow fiashthe said glow-discharge'lamp, means for connecting the said glow lamp with the output circuits of said vacuum tubes,.means to bias the tubes so that only av small residual'current flows therethrough in the absence of impressed signals, means for applying signals to the input circuits'of said vacluuntubes, and means for superimposing the output signals :tromsaid vacuumtubes upon said biasing potential to said glow lamp.

2. A stabilizingv means for glow-discharge tubescomprising a glow discharge tube, a

pair of thermionic amplifiers having paralel ly' connected outputs, a source of plate potential for said amplifiersconnected in series with said glow lamp. andsaid amplifiers for normally maintaining said glow discharge tubeabove the flash potential, biasing means for normally biasing the input electrode of that only a small residual current will'flow therethrough, and means for differentially supplying signalpotentials tothe input circuits of said thermionic tubes, whereby the upon said glow tube v and the intensity of illuminationtof said glow tube is varied in proportion to the strength of incoming signal impulses.

3. A system for representing current values as light intensities including a plurality of vacuum tube amplifiers having their output lamp of a value sufficient to continuously electrodes connected in parallel, means for V impressing signals differentially upon the input circuits of said vacuum tubes, means" for biasing said tubes to a point where only a small residual current flow occurs therethrough in theabsencei of signals, a glow discharge lamp connected in the outputcircuit of said amplifiers, a source of high potential' connected in series with said glow lamp and each of said amplifiers, said source of potential being of a value above that required for producing an initial glow insaid glow lamp,-said output circuit providing each of said thermionic tubes to such a point -r1 amplified signal potentials are impresseda path for impressing amplified signals from said amplifiers upon said glow lamp whereby fluctuations in the signals appearing in the output circuit of said amplifiers produces proportionate changes in the intensity of glow in said glow lamp.

4. An arrangement for stabilizing glowdischarge tubes which comprises a pair of vacuum tubes having their outputs in parallel, a glow-discharge tube in the common output circuit of said vacuum tubes, means to bias the tubes so that only a small residual current flows therethrough in the absence of impressed signals, and means for differentially supplying signal potentials to said Yacuum tubes whereby current fluctuations in the output circuits of said tubes produce proportionate intensity fluctuations in said glowdischarge tube.

5. A stabilizing system for glow discharge tubes comprising a pair of thermionic'tubes having their output circuits in parallel connection, means to bias the tubes so that only a small residual current flows therethrough in 5 the absence of impressed signals, means to supply signals differentially to the input circuit of each of said tubes, and a glow dis charge tube included in the parallel output circuit of said tubes, said glow discharge tube being responsive to the amplified signal input to produce changes in the intensity of glow therefrom. V

OTTO SCHRIEVER. 

